Diagnosing Stable Angina
Diagnosis of stable angina begins with a detailed clinical history characterizing chest pain quality, location, duration, and relationship to exertion, followed by cardiovascular risk factor assessment and pretest probability estimation to guide further testing. 1
Clinical History: The Foundation of Diagnosis
The clinical examination is the key first step and should include detailed assessment of chest pain characteristics 1:
Chest Pain Characterization
Typical angina must meet all three criteria: 1
- Substernal chest discomfort with characteristic quality and duration
- Provoked by exertion or emotional stress
- Relieved by rest or nitroglycerin
Atypical angina meets only two of these characteristics. 1
Noncardiac chest pain meets one or none of these characteristics. 1
Pain Quality and Location
Anginal pain is typically described as "squeezing," "griplike," "suffocating," or "heavy"—rarely as "sharp" or "stabbing," and it does not vary with position or respiration 1. The location is usually substernal, with radiation to the neck, jaw, epigastrium, or arms 1. Pain above the mandible, below the epigastrium, or localized to a small area over the left lateral chest wall is rarely angina 1.
Important caveat: Women and elderly patients frequently present with atypical symptoms including sharp chest pain, nausea, vomiting, or midepigastric discomfort rather than classic anginal descriptions 1.
Duration and Triggers
Anginal pain typically lasts minutes, is precipitated by exertion or emotional stress, and is relieved by rest 1. Sublingual nitroglycerin usually relieves angina within 30 seconds to several minutes 1.
Risk Factor Assessment
After characterizing chest pain, assess cardiovascular risk factors 1:
- Smoking
- Hyperlipidemia
- Diabetes mellitus
- Hypertension
- Family history of premature coronary artery disease (onset in male first-degree relative <55 years or female <65 years)
- History of cerebrovascular or peripheral artery disease
Physical Examination
The physical examination is usually normal or nonspecific in patients with stable angina but may reveal related conditions such as heart failure, valvular heart disease, hypertrophic cardiomyopathy, or peripheral vascular disease 1. An audible rub suggests pericardial or pleural disease 1. Evidence of vascular disease includes carotid or renal artery bruits or diminished pulses 1.
Pretest Probability Estimation
The data gathered during clinical evaluation must be used to determine the patient's probability of having ischemic heart disease, which then guides subsequent evaluation. 1
The probability of coronary artery disease is estimated based on: 1
- Characteristics of chest pain (typical vs. atypical vs. noncardiac)
- Patient's age
- Patient's sex
- Presence of cardiovascular risk factors
Testing Strategy Based on Pretest Probability
When pretest probability is <5%, further testing is usually not needed because the likelihood of false-positive results is substantial. 1
When pretest probability is >90%, the probability of false-negative results is high, making testing less useful. 1
Intermediate pretest probability (10-90%) is the optimal range for diagnostic testing. 1
Differential Diagnosis and Precipitating Factors
Systematically evaluate for conditions that may precipitate angina by increasing myocardial oxygen demand or decreasing oxygen supply 1:
Conditions increasing oxygen demand: 1
- Hyperthermia with volume contraction
- Hyperthyroidism
- Cocaine abuse or sympathomimetic toxicity
- Severe uncontrolled hypertension
- Hypertrophic cardiomyopathy
- Aortic stenosis
Conditions decreasing oxygen supply: 1
- Anemia
- Hypoxemia from pulmonary disease
- Polycythemia, leukemia, thrombocytosis, or hypergammaglobulinemia
Laboratory Investigations
Basic laboratory tests should include 1:
- Lipid profile assessment
- Fasting glucose or hemoglobin A1c for diabetes screening
- Complete blood count (hemoglobin assessment)
- Serum creatinine for renal function evaluation
Electrocardiography
Resting electrocardiography should be performed as part of the initial evaluation 1. While often normal in stable angina, it may reveal evidence of prior myocardial infarction, left ventricular hypertrophy, or conduction abnormalities that influence prognosis and management 1.
Critical Distinction: Stable vs. Unstable Angina
Patients presenting with acute angina must be categorized as stable or unstable. 1 Those with symptoms consistent with unstable angina (new onset, increasing in frequency/intensity/duration, or occurring at rest) should be further classified by short-term risk 1. Patients at high or moderate risk should be promptly transferred to an emergency department for evaluation and treatment 1.